RuAviation

At the beginning of June, flight certification tests of the first SJ-100 prototype airplane with flight number 97021 started at the Gromov LII airfield. The program envisages a gradual increase in the intensity of flights, but their increase is constrained by the PD-8 engine, which is replacing the French-Russian SaM146.

It will be possible to reach the set volume of the flight program with the connection of two additional prototypes to the flights. As Rostec CEO Sergei Chemezov told the Federation Council plenary session on October 23, the PD-8 engine is at the final stage of development, and bench tests are currently underway. Upon their completion, the engine will be certified as part of the experimental SJ-100 in 2025.

Much of the work to create a virtually new airplane in the familiar Sukhoi Superjet 100 fuselage shape is invisible to the public. In addition to flight tests, certification includes engineering studies, comprehensive calculations, bench and strength tests, as well as qualification of materials, software and component parts. Kirill Kuznetsov, Chief Designer of the SJ-100, explained how exactly the work on certification of this model is proceeding, compared to the testing of the SSJ100 airplane, and explained that the scope of work should be evaluated by dividing it into two groups: “the airplane as an aircraft” and ‘the airplane and its systems’.

“For the first group it is necessary to carry out approximately 30-40% of the volume of tests previously performed during SSJ100 certification. The relatively small volume is explained by the fact that when creating the new modification, we kept the theoretical outline, aircraft and systems architecture unchanged, as well as system interfaces as much as possible. Accordingly, a significant part of the checks do not require re-validation. In particular, this applies to a colossal volume of tests related to aerodynamics, stability and controllability,” Kirill Kuznetsov told the UAC press service.

But for the “airplane and its systems” group, the volume of tests reaches up to 90% of the previous ones conducted by Sukhoi Civil Aircraft. Now the main focus is on bench tests, which require confirmation of compliance with new technical requirements.

AP-21 aviation regulations serve as the basis for certification of aircraft in Russia, ensuring compliance with safety requirements. At the initial stage of the project, a certification baseline is formed, which defines the points of safety requirements and methods of their assessment. In the case of the import-substituted Superjet, the main document becomes the RRJ-95 Certification Basis – this is how the SSJ100 is designated in the technical documents.

“The requirements of the Certification Basis apply to all levels of cooperation, from the lead developer to the manufacturers of systems and components. After a detailed decomposition of requirements, a certification work program is drawn up, which defines the sequence of actions for safety compliance,” Kirill Kuznetsov explained.

In order to achieve compliance with modern safety requirements, it is necessary to test prototypes, work out detailed design changes based on the obtained data and issue full certification documentation. The process of integrating new systems is accompanied by a number of difficulties.

“One of the factors is the high degree of novelty of technological solutions faced by the enterprises participating in the cooperation. Many of them do not have sufficient experience in systematic qualification work for components, which, in turn, slows down the overall process of systems adaptation to the aircraft,” explained the SJ-100 chief designer for the significant postponement of the start of serial production and operation of the aircraft.

He added that a separate complicated topic is the PD-8 engine. “I won’t hide, the situation has significantly affected our plans,” Kirill Kuznetsov said, highlighting two aspects of such influence.

The first is related to the demonstration of the aircraft’s takeoff and landing characteristics, as well as the evaluation of the engine itself in order to obtain materials to establish the suitability of the marshalling power plant as part of the aircraft. The second is the interaction of the engine with other systems, which is verified during testing on the 97021. At the same time, much of the testing is conducted on stands, so the designers do not expect serious problems here.

The flight test program was delayed due to the unpreparedness of the engine. Now all systems and components are being tested on the first prototype aircraft (b/n 97021), which is equipped with SaM146 engines.

“We are today trying to fly systems and components as much as possible on the first prototype aircraft, which is equipped with SaM146 engines. The goal: to enable our co-implementers to complete their qualification work and “freeze” the design. It is important for us that the production of products to complete serial aircraft does not require any additional rework and, accordingly, does not negatively affect the work of our production center in Komsomolsk-on-Amur,” said Kirill Kuznetsov.

After the PD-8 engines are installed on the aircraft, a methodological council will be held, which will issue a permit to connect the second and third prototype aircraft to the flight test program.